Fifth gear of MT popping out

Hi,

I have researched this subject on my car and found that the fifth gear can be accessed by a side access panel on the manual transmission. I found a kit online to replace the fifth gear, which included the following parts:

Fifth gear 40 teeth, 33336-42040

Internal split needle bearing, 90364-28023

Outer synchro hub sleeve, 33395-42012

Transmission hub fifth gear 33393-42010

I have replaced these parts and topped off the gear oil, but it still pops out of fifth gear. I have to hold the shifter into fifth so it does not pop out, but when I hold it there it feels more firm than it did before I replaced the above parts. I have also inspected shift linkages for a bent fifth gear linkage rod or bad linkage bushings. The fifth gear linkage rods and bushings looked good with no bent rods or worn out bushings.

The only other thing I think it could be is the synchronizer rings. From my research, people often replace the parts above and keep the original inner synchronizer rings that go inside the fifth gear transmission hub and that often would fix the fifth gear. Could worn synchro rings be the cause of the fifth gear still popping out? Are there specific syncro rings that could cause it to pop out of fifth?

Here are the three synchro ring part numbers for my car I've looked at replacing:

Toyota 33396-12011 - RING, SYNC

Toyota 33397-12011 - RING, SYNC

Toyota 33399-12011 - RING, SYNC